Magnetic anchoring device for graphic arts

ABSTRACT

Magnetic anchoring device for graphic arts, wherein the magnetic work surface is provided by interposing permanent magnetic cores between ferromagnetic material pole-pieces, having a direction of magnetization for the cores substantially at right angles to said pole-pieces. The device comprises a support of ferromagnetic material having a plurality of parallel slots separated by walls defining a first plurality of pole-pieces fast with said support, a spacer of a magnetic material being placed in each of said slots, and each of said slots having therein a permanent magnet battery or unit comprising an inserted central wall or core of ferromagnetic material which is interposed between two side permanent magnetic elements. The assembly of said inserted walls define a second plurality of pole-pieces alternately interposed to the first plurality of pole-pieces. The surfaces of the magnetic elements contacting each of said inserted walls have always the same polarity, so that the magnetic surface being provided has pole-pieces of one polarity intercalated with polepieces of opposite polarity to said one polarity.

United States Patent [191 Cardone et al.

[451 Jan. 15, 1974 MAGNETIC ANCHORING DEVICE FOR GRAPHIC ARTS [76] Inventors: Michele Cardone, Via Boschetto,

l9, Trezzano S.N.; Angelo Grandini, Via Oratorio 44, Pero; Bruno Zaramella, Via Cascina Barocco 18, Milan, all of Italy [22] Filed: June 22, I972 [21] Appl. No.: 265,198

[52] US. Cl. 335/295, 335/306 [51] Int. Cl. 110 7/04 [58] Field of Search 335/285, 295, 306

[56] v References Cited UNITED STATES PATENTS 2,269,l49 l/l942 Edgar 335/295 FOREIGN PATENTS OR APPLICATIONS 933,666 8/1963 Great Britain 335/285 Primary Examiner-George Harris Attorney-Jennings Bailey, Jr.

[57] ABSTRACT Magnetic anchoring device for graphic arts, wherein the magnetic work surface is provided by interposing permanent magnetic cores between ferromagnetic material pole-pieces, having a direction of magnetization for the cores substantially at right angles to said polepieces. The device comprises a support of ferromagnetic material having a plurality of parallel slots separated by walls defining a first plurality of pole-pieces fast with said support, a spacer of a magnetic material being placed in each of said slots, and each of said slots having therein a permanent magnet battery or unit comprising an inserted central wall or core of ferromagnetic material which is interposed between two side permanent magnetic elements. The assembly of said inserted walls define a second plurality of polepieces alternately interposed to the first plurality of pole-pieces. The surfaces of the magnetic elements contacting each of said inserted walls have always the same polarity, so that the magnetic surface being provided has pole-pieces of one polarity intercalated with pole-pieces of opposite polarity to said one polarity.

8 Claims, 7 Drawing Figures MAGNETIC ANCl-IORING DEVICE FOR GRAPHIC ARTS This invention relates to a magnetic device for use in graphic arts for anchoring plates or cliches and the like in place of the conventional anchorage as accomplished by glueing on so called systematic blocks involving a long and difficult operation, mostly causing the loss of the plate after the first use.

The introduction of modern printing systems has developed novel plates (hyloprint method and the like), having a ferro-magnetic supporting base which in addition to conventional anchorage by adhesives, can be fixed by using suitably designed magnetic planes.

However, the magnetic planes as used at present have a work surface characterized by a limited number of magnetic fields, the field strength and depth of which are additionally quite inadequate to the intended purpose, as not exerting enough anchorage power on the plates, so that stresses acting on the latter would tend to shift the same relative to the magnetic anchoring plane, causing drawbacks during the printing cycle because of phase-difference in colour overlap, and additionally known magnetic planes have not the required mechanical strength.

Thus, when designing such magnetic planes, both the particular work conditions and the characteristics of the component on which the magnetic effect is developed should be duly taken into account. The work conditions are essentially characterized by substantial mechanical compressive and drawing stresses normally developed according to a direction parallel to the mag netic anchorage surface, causing the above mentioned drawbacks, because of the features of the ferromagnetic plate component, which can be summarized in a highly limited thickness, 0.3 mm at the most, and relatively large bearing surface.

This being stated in advance and duly taking into account the particular requirement in this art and the drawbacks in the conventional planes, the magnetic anchoring device according to the invention was designed and carried into effect.

The ideal features of a magnetic anchoring device for graphic arts can be summarized as follows: an unusual fastening strength of the ferromagnetic plate component. Such a strength can be achieved only by acting on a high number of magnetic fields which are characterized by a considerable field strength adjacent the air gap as built up at the work surfaces of the magnetic plane and a field depth which is much reduced and such that the ferromagnetic material section of said component is never exceeded. Full use of said fastening strength at work conditions, this involving athorough shielding of the magnetic fields in all of the plane locations not concerning the work surface. A considerable mechanical strength enabling the device to fully endure the heavy stresses it is subjected to during use.

Therefore, bearing such features in mind, the magnetic device according to the invention could be carried into effect, which device, by using a magnetic material properly suited to the purpose and by a suitable design of the magnetic circuit, provides a considerable improvement in the actual work conditions of the magnetic device.

The magnetic device for graphic arts according to the invention, in which the magnetic work surface is provided by interposition of permanent magnetic cores between the pole-pieces made of ferromagnetic material with the direction of magnetization for the cores perpendicular to the pole-pieces, comprises a support of ferromagnetic material having a plurality of parallel slots separated by walls defining a first plurality of polepieces fast with said support; a spacing element of amagnetic material being provided on the bottom of each of said slots and a magneto-permanent battery being inserted in each slot and comprising a wall or central core as a ferromagnetic material insert being interposed between two side permanent magnetic elements, the assembly of said inserted walls defining a second plurality of pole-pieces interposed relative to the first mentioned pole-pieces, and the surfaces of said magnetic elements contacting each of said inserted walls having still the same polarity, whereby the magnetic surface so formed has pole-pieces of a given polarity intercalated to pole-pieces having a polarity opposite to said given polarity.

A further feature of the magnetic device according to the invention consists of using oriented or not oriented plastic-ceramic material for the permanent magnets, enabling to maintain the air gaps and pole-pieces to minimal sizes, thus allowing to provide a suitable number of magnetic fields on the work surface of said plane, taking the maximum advantage of the magnetic characteristics of said material. As required, the magnetic anchoring device can be provided as a plane or a cylinder.

These and other features of the magnetic anchoring device according to the invention will be more clearly understood from the following description with reference to the accompanying drawings, in which:

FIG. 1 is a plan view showing a general magnetic plane according to the invention;

FIG. 2 is a sectional view taken along line 22 in FIG. 1;

FIG. 3 is a sectional view taken along line 3-3 in FIG. 2;

FIG. 4 is an enlarged'fragmentary sectional view, substantially taken along line 22 in FIG. 1, showing the supporting base only;

FIG. 5 is an enlarged view showing a permanent magnet battery or unit, as incorporated in the magnetic plane according to the invention;

FIG. 6 is an enlarged detailed view showing a modified magnetic plane according to the invention; and

FIG. 7 is a fragmentary sectional view of a magnetic cylinder according to the invention.

Referring to FIGS. 1-5, it will be seen that a general magnetic plane according to the invention substantially comprises a base 10 of high permeability, ferromagnetic material, at the top of which slots 11 are formed, such as by milling, these slots 11 being parallel to one another and at regular spacing (FIG. 4) and having a substantially rectangular cross-section, being separated from one another by walls 12 at right angles to the plane of said base. Thus, said walls 12 form a first plurality of pole-pieces which are fast with the base of said magnetic plane.

A spacer 13 of amagnetic material, such as aluminum, is placed on the bottom of each slot 11, then placing a permanent magnet battery or unit, of the type as shown in FIG. 5, and comprising an intermediate wall or core 14 of high permeability, ferromagnetic material, laterally of which two permanent magnetic cores or elements 15 and 16 are placed, as magnetized in a cross direction to the core 14 or slot 11. This spacer 13 serves the purpose of avoiding shortcircuits between the inserted elements or pole-pieces 14 and the slot bottom.

-As it will be seen from FIG. 2, the depth of each slot 11 is the same as the height of the inserted pole-piece 14 plus the thickness of the amagnetic spacer l3; correspondingly, the width of each slot 1 1 is equal to the sum of the widths of the magnetic elements l5, l6 and polepiece 14. Moreover, it will seen from FIGS. 2 and 4 that the height of the magnetic cores l5 and 16 is slightly less that that of the inserted pole-piece 14, so as to form a air-gap between the polepiece 12 fast with base and the corresponding inserted pole-pieces 14.

In order to provide for the proper configuration of the magnetic field at the work surface 18 of the so formed magnetic plane, each of said permanent magnet battery or' unit are provided so that the surfaces of the two magnetic elements 15 and 16 contacting the corresponding surfaces of the inserted pole-piece 14 are always of the same sign or polarity, as show, in FIG. 5, so as to form at said work surface 18 a first plurality of pole-pieces 12, all of which of the same sign or polarity, and a second plurality of pole-pieces 14 which are intermediate and of a sign or polarity opposite to that of the first mentioned pole-pieces.

This assembly comprising each permanent magnet battery or unit is made fast by using an epoxy resin of a high adhesiveness and low viscosity, previously spread on allof the surfaces contacting the permanent magnetic elements and said pole-pieces. Correspondingly, the grooves being formed at each air gap 17, because of the permanent magnetic elements 15 and 16 being of a slightly less height than the pole-pieces, as above mentioned, are then tilled with a second epoxy resin, characterized by a high hardness, such as ST. 29 marketed by The Vagnone & Boeri or equivalent resin, to provide a work surface of even hardness and avoid shortcircuits in the magnetic material being used, which shorts would be unavoidable where said magnetic material should contact the ferromagnetic component to be anchored.

This magnetic plane is then subjected to fixing by grinding the work surface 18, perimetral surface and base surface.

' However, the features of the magnetic plane according to the invention are not only due to its particular structure, but also to the use of suitable material for the permanent magnetic elements 15 and 16.

Thus, it was found that to achieve the best performances of the magnetic plane according to the invention, the magnetic elements 15 and 16 should be formed of oriented or not oriented magnetic ceramic-plastic material, such as that known by the trade name Plastiform and marketed by The Layman Corporation Magnetics Division, Ohio, U.S.A. Of course, other magnetic materials to the purpose could be found.

As to the sizing of the several parts comprising the above described magnetic plane, it was found that the best performances are achieved with magnetic cores having a thickness in the direction of magnetization not exceeding 2 mm. and pole-pieces not thicker than 2 mm., the total width for each slot not exceeding therefore 6 mm. It is also specified that the optimum thickness for each spacer 13 should be equal to the air gap size and the ratio of the pole length to the ideal magnetic length should be about 511, where magnetic length is the thickness in the direction of magnetization and pole length is that in a direction at right angles to the former.

The advantages of the plane for graphic arts according to the invention can be summarized as follows.

Use of a highly suitable magnetic material (Plas tiform) for this particular application which. owing to an ideal ratio of the polar surface to the magnetic length has its operative point comparatively adjacent that of residual induction(Br). Moreover, the magnetic return curve is coincident with the magnetization curve, whereby no re-magnetization is required following the preparation of the pole-pieces, operation which would be quite unpractical. The minimized sections and the highly versatile mechanical characteristics of this material enable to provide a much limited air gap and an excellent connection between magnetic material and pole-pieces with a resulting highly reduced drop of the magnetomotive force theoretically obtainable. Finally, a relatively high power product is provided.

The high magnetic permeability steel pole-pieces, such as PE. 37, according to calculated sizes in function of the dimensional characteristics of said magnetic core and of the particular application of the obtained equipment, allow a proper exploitation of the magnetomotive force provided by the magnetic material, converting to a magnetic field of a high strength and higly reduced depth.

The high number of magnetic fields on the work surface (with air gaps as long as 2 mm. or less) allows a considerable increase in the anchoring power within a properly defined work surface not having any magnetically dead zone.

Additionally, the ferromagnetic material base, fast with just the half of the pole-pieces, enables a correct shielding of the magnetic circuits and complete freedom thereof of damages. It also provides for an increased mechanical strength of the plane.

Advantageously, each of the inserted pole-pieces could comprise two possible symmetrical parts 14. and 14" separated by a longitudinal plane, as diagrammatically shown in FIG. 6, so as to emphasize the magnetic performances of the plane, since each magnet would substantially have its own path for the available magnetomotive force.

A further variant is shown in FIG. 7, where it will be seen that the magnetic anchoring device is in the form of a magnetic cylinder having a cylindrical support 20 of ferromagnetic material, on at least part of the outer cylindrical surface of which parallel-sided longitudinal slots 21 have been milled, in each of which a magnet permanent unit 22, substantially identical to that used for the magnetic plane in the preceding figures, has been inserted and secured by adhesive agents. Since the magnetic circuit is substantially unaltered, the dimensional characteristics of the latter, as referred to this magnetic cylinder, will be substantially unaltered or similar to those above mentioned, so as to achieve the best results.

What is claimed is:

l. A magnetic anchoring device for graphic arts, wherein the magnetic work surface is provided by permanent magnetic cores interposed between ferromagnetic material pole-pieces, having a direction of magnetization for the cores substantially at right angles to said pole-pieces, characterised by comprising a support of ferromagnetic material having a plurality of parallel slots separated by walls defining a first plurality of pole pieces fast with said support; a spacer of non-magnetic material positioned in each of said slots, and each of said slots having therein a permanent magnet battery means comprising an inserted central core means of ferromagnetic material which is interposed between two side permanent magnetic elements, the assembly of said inserted walls defining a second plurality of polepieces alternately interposed to the first plurality of pole-pieces; the surfaces of the magnetic elements contacting each of said inserted walls having always the same polarity, so that the magnetic surface has polepieces of one polarity intercalated with pole-pieces of opposite polarity to said one polarity.

2. A magnetic anchoring device as claimed in claim 1, wherein such magnetic elements are of ceramicplastic material.

3. A magnetic anchoring device as claimed in claim 1, wherein said polel-pieces are of a thickness not exceeding 2 mm.

4. A magnetic anchoring device as claimed in claim 1, wherein the height and thickness of each of said magnetic elements are not over 10 mm. and 2 mm., respectively.

5. A magnetic anchoring device as claimed in claim 1, wherein the air gap length between two adjoining pole-pieces is not over 2 mm.

6. A magnetic anchoring device as claimed in claim 1, wherein each of said inserted pole-pieces are longitudinally divided into two halves.

7. A magnetic anchoring device as claimed in claim 1, wherein the configuration thereof is planar.

8. A magnetic anchoring device as claimed in claim 1, wherein the configuration thereof is cylindrical. 

1. A magnetic anchoring device for graphic arts, wherein the magnetic work surface is provided by permanent magnetic cores interposed between ferromagnetic material pole-pieces, having a direction of magnetization for the cores substantially at right angles to said pole-pieces, characterised by comprising a support of ferromagnetic material having a plurality of parallel slots separated by walls defining a first plurality of pole pieces fast with said support; a spacer of non-magnetic material positioned in each of said slots, and each of said slots having therein a permanent magnet battery means comprising an inserted central core means of ferromagnetic material which is interposed between two side permanent magnetic elements, the assembly of said inserted walls defining a second plurality of pole-pieces alternately interposed to the first plurality of pole-pieces; the surfaces of the magnetic elements contacting each of said inserted walls having always the same polarity, so that the magnetic surface has pole-pieces of one polarity intercalated with pole-pieces of opposite polarity to said one polarity.
 2. A magnetic anchoring device as claimed in claIm 1, wherein such magnetic elements are of ceramic-plastic material.
 3. A magnetic anchoring device as claimed in claim 1, wherein said pole-pieces are of a thickness not exceeding 2 mm.
 4. A magnetic anchoring device as claimed in claim 1, wherein the height and thickness of each of said magnetic elements are not over 10 mm. and 2 mm., respectively.
 5. A magnetic anchoring device as claimed in claim 1, wherein the air gap length between two adjoining pole-pieces is not over 2 mm.
 6. A magnetic anchoring device as claimed in claim 1, wherein each of said inserted pole-pieces are longitudinally divided into two halves.
 7. A magnetic anchoring device as claimed in claim 1, wherein the configuration thereof is planar.
 8. A magnetic anchoring device as claimed in claim 1, wherein the configuration thereof is cylindrical. 